Process for soil conditioning by aerial application of water soluble or swellable polymers

ABSTRACT

Process for soil conditioning includes applying to the soil a composition comprising at least a water soluble or swellable polymer. The composition has a particulate form and is applied by an aerial application. The process is suitable for soil conditioning and for reduction in soil erosion in agriculture, forestry, construction and civil engineering, mining, water storage and transportation, protection of rivers and delta against pollution, environmental conservation.

TECHNICAL FIELD OF THE INVENTION

The present invention is directed to a process for soil conditioning byapplying at least one polymer on its surface.

Soil conditioning allows to preserve its integrity, to improve or topreserve its properties and to preserve environment and people bylimiting elements transfers by hydraulic or aerial way. These benefitsare obtained by protecting structural stability of aggregates, bylimiting erosion and slaking phenomena, thus leading many side benefits.

The term “soil conditioning” encompasses the erosion control by water orwind path, formation control of slacking crusts, preservation of soilaggregate structure, water infiltration and diffusion control,modification of hydrophobic or hydrophilic properties of soils,restoration of sodic and alkaline soils, water turbidity control offlooded crops, transfer control of contaminants, but not limited tothese uses.

The technical field in which is applied soil conditioning is mainlyagriculture but also forestry, construction and civil engineering,mining, water storage and transportation, protection of rivers and deltaagainst pollution, environmental conservation and other fields.

BACKGROUND

Following the Second World War, polymers, generally water soluble, wereused to stabilize soils. Scientific literature, in the 50s, describesthe use of different soil conditioning polymers as the Krilium® of theMonsato Chemical Company.

Several other polymers have been described afterwards to conditionsoils:

-   -   Synthetic polymers: for instance, homopolymers and copolymers of        acrylamide, acrylic acid and its salts, methacrylic acid and its        salts, acrylonitrile, vinylpyrolidone, vinylformamide,        2-acrylamido-2-methyl propane sulfonic acid and its salts, vinyl        acetate, maleic acid or ethylene oxide and derivatives likes        hydrolysed polyacrylonitrile, polyvinyl alcohol;    -   Natural polymers, natural gums, polysaccharides and their        derivatives: galactomannan, guar gum, carob gum, xanthan gum,        arabic gum, chitosan, carrageenan, pectins, starch, modified        starches, alginates, celluloses, cellulose derivatives        (cellulose ethers), agar-agar;    -   Grafted polymers: for instance, starch-acrylamide-acrylates,        starch-acrylonitrile, chitosan-acrylic acid copolymers.

Among all these polymers, polyacrylamides have been the focus ofresearch and have been adopted for their efficiency in soilconditioning, reduction of soil erosion, increased water quality postirrigation and their low cost.

Polyacrylamide added to irrigation water has proven to decrease soilerosion drastically. Lentz and al. have applied polyacrylamide dosesfrom 1 to 20 ppm in irrigation water (furrow irrigation) and havecontrolled erosion by 96% with the 10 ppm dose. Literature is abundantfor this topic including the following article: “preventing irrigationfurrow erosion with small application of polymers” published in the SoilScience Society of America Journal (1992, issue 56, pages 1926-1932).

The application of polyacrylamide (PAM), reduces the redistribution offine soil particles in irrigation or rain water and prevents theformation of crust on the soil surface. Crust formation is caused bysoil fines clogging the soil pores, leading to the formation of animpervious layer that restricts water and air movement into the soilprofile. Seedlings have difficulty breaking through the crust, limitingthe crops emergence. Seedling emergence can be improved by anapplication of polyacrylamide before the first rain event or prior toduring the post-planting irrigation application.

The ability of polyacrylamide to flocculate the solids out of theirrigation and runoff water also prevents the discharge of nutrients andpesticides which have attached to the soil particles. By limiting theamount of soil, nutrient, and pesticide runoff, polyacrylamide helpsimprove the water quality post-irrigation, reduces the turbidly of thetail water, and helps improve the “health” of the drainage ecosystem.For these reasons polyacrylamide is a valuable conservation tool used toaddress the water quality in production agriculture.

By binding smaller particles together, polyacrylamide helps increase theparticle size. The larger particle size decreases pore clogging,increases soil uniformity, and increases infiltration rates. All ofthese factors allow for better wetting of the soil profile and moreefficient use of water, which can lead to yield increases and a decreasein irrigation cost.

Water soluble polymers have several benefits as described above.However, their application on the soil is limited to irrigation periodsand it is often limited by the number of irrigation cycles during thegrowing season. Currently irrigation water is the primary method ofapplication of these products.

If the irrigation water source is a canal water, typically the water istreated in the canal using the dry form of polyacrylamide and is appliedusing a granular applicator. The polymer is dosed into the water and thewater is pulled out the canal.

If the irrigation water is a well, polyacrylamide, in emulsion form isinjected either at the well head or in-field riser. The riser being thepoint in the field where the water is delivered. In most cases, a wellsupplies multiple risers for a total of 140 to −200 acres on average.

The delivery of the water from the canals and wells differs inapplication. Most canal irrigated scenarios use a form of suction tubeto pull water out of the canal. Each tube is placed in either every rowor every other raw. In a well scenario the water is pumped out of theriser in a “Poly pipe”. Poly Pipe is a large inflatable roll of plasticpipe than runs along the high side of a field. The irrigator then pokesholes in the pipe to release the water. The number of holes and spacingof holes are determined by the target volume raw spacing. A computerprogram is typically used to determine the size and number of holes in arun of Poly pipe.

Patent application PCT/FR2014/051863 describes a soil conditioningprocess to apply a water or swellable polymer to the soil consisting inpreparing polymer in a concentrated liquid form and in applying thispreparation on the surface of a support in rotation around its axis ofrevolution in order to create droplets which are spreaded to the soil.This process allows to apply soil conditioning polymer withoutirrigation system but the concerned support in rotation is fixed forinstance on a tractor and so application is time consuming if largesurfaces have to be treated.

TECHNICAL PROBLEM SOLVING

These polymers are more efficient if they are applied during the initialirrigation or prior to a rain event. In cases where irrigation is theprimary source of water, it is typically much easier to control thetiming of the application but is still expensive due to the amount oftime and equipment needed to meter the polymer. Electricity is notalways available to power pumps; this reduces the ability to properlydeliver the polymer. Polymers are often packaged in 30 gallon drums orlarge 275 gallon totes bins which are difficult to handle in fields, andlong term in-field storage can reduce the effectiveness of the product.In regions where rainfall is the primary source of water, the ability toapply PAM to the soil, post-planting but before a rain event, is nearimpossible, with traditional application mean.

There is still a problem to apply water soluble or swellable polymers ina timely manner because of amount of time and equipment.

DESCRIPTION OF THE INVENTION

The present invention intends to solve the problem previously described.

The object of the invention is a process for soil conditioningconsisting of applying by an aerial application to the soil, acomposition in particulate form, said composition comprising at least awater soluble or swellable polymer.

In the following of the description, “particulate form” means powder,bead, tablet, prill or a mixture thereof having a size preferablybetween 0.1 and 10 millimeters, advantageously between 0.5 and 4millimeters.

Polymer Description

The composition applied in the process of the invention comprises atleast a water soluble or swellable polymer.

A “water soluble polymer” is a polymer which gives a solution withoutinsoluble particles when it is dissolved under agitation at 25° C. andwith a 50 g/L concentration in water.

A “water swellable polymer” is a polymer which swells and thickenssolution when it is put in water at 25° C.

Water soluble or swellable polymers are selected from the groupcomprising:

-   -   Homopolymers and copolymers of acrylamide, acrylic acid and its        salts, methacrylic acid and its salts, acrylonitrile,        2-acrylamido-2-methyl propane sulfonic acid and its salts,        vinylpyrolidone, vinylformamide, vinyl acetate, maleic acid or        ethylene oxide and derivatives likes hydrolysed        polyacrylonitrile, polyvinyl alcohol;    -   Natural polymers, natural gums, polysaccharides and their        derivatives: galactomannan, guar gum, carob gum, xanthan gum,        arabic gum, chitosan, carrageenan, pectins, starch, modified        starches, alginates, celluloses, cellulose derivatives        (cellulose ethers), agar-agar;    -   Starch-acrylamide-acrylates, starch-acrylonitrile,        chitosan-acrylic acid copolymers.

For the process of the invention, polymers or copolymers of acrylamideare the most interesting.

Polymers of the invention can be linear, structured or cross-linked. Theterm structured polymers signifies polymers in branched, star or combform.

Branched polymers are classically not linear polymers with lateralchains. Cross-linked polymers are classically not linear polymers undera tri-dimensional array form, insoluble in water, but which swell inwater.

Polymers of the invention are preferably anionic. Their anionic chargecontent is preferably between 5 and 60 mol %.

Water soluble or swellable polymers may be prepared by reacting monomeror monomer blend under polymerization in conventional manners known aperson of the art.

Then, they can be obtained in form of powder, bead, suspension, inverseemulsion or liquid.

In a preferred embodiment of the invention, water soluble or swellablepolymers are homopolymers or copolymers of acrylamide.

Acrylamide based polymers are obtained by polymerization of acrylamideand other water-soluble monomers with a ethylenically unsaturated moietyselected from the following families:

-   -   Anionic monomers. They are advantageously selected in the groups        comprising monomers with an acid carboxylic moiety (e: acrylic        acid or methacrylic acid and their salts . . . ), monomers with        a sulfonic acid moiety (ex: 2-acrylamido-2-methyl propane        sulfonic acid (AMPS) and its salts . . . ).    -   Non-ionic monomers. They are advantageously selected in the        group comprising methacrylamide, acrylamide derivatives likes        N-alkylacrylamide, as for instance N,N-dimethylacrylamide or        methylolacrylamide. vinylformamide, N-vinylpyridine,        N-vinylpyrrolidone, hydroxyalkyl(meth)acrylates and        (meth)acrylates with an alkoxy chain can also been used.    -   Cationic monomers. They are preferably selected in the groups        comprising diallyldialkyl ammonium salts likes diallyldimethyl        ammonium chloride (DADMAC) and dialkylaminoalkyl (meth)acrylates        likes dimethylaminoethyl (meth)acrylate ((M)ADAME) and their        acidified or quaternized forms by means known by the skill man        of the art., and also dialkylaminoalkyl (meth)acrylamide and        their acidified or quaternized forms likes the (meth)acrylamide        propyl trimethyl ammonium chloride (((M)APTAC).    -   Zwitterionic monomers can also been used. Anionic and cationic        charges are associated on one single monomer. Example of        zwitterionic monomers: sulfobetains likes sulfopropyl        dimethylammonium ethylmethacrylate, sulfopropyl dimethylammonium        propylmethacrylamide or sulfopropyl 2-vinylpyridinium,        phosphobetains likes phosphato ethyl trimethylammonium        ethylmethacrylate and carboxybetains.

Preferably, water soluble or swellable polymers present in thecomposition of the invention are in powder or bead form.

In a preferred embodiment of the invention, polymers are water solublepolymers.

Preferably, molecular weight of water soluble polymers is above 500 000g·mol⁻¹ and preferably between 1 and 30 million g·mol⁻¹, and morepreferably above 5 million g·mol⁻¹.

Composition Description

In the process of the invention a composition is applied by an aerialapplication.

The composition has a particulate form and comprises at least one watersoluble or swellable polymer and optionally at least one othercomponent.

The composition contains preferably between 20% and 100% and preferablybetween 50 and 100% by weight of water soluble or swellable polymers.

Preferably, water soluble and swellable polymers are in powder or inbead form.

To improve the spreading of the composition, the composition is inpowder form and has a particle size between 0.1 and 10 millimeters,preferably between 0.5 and 4 millimeters. Particle size refers to themean diameter measured with a laser particle sizer accordingconventional technics known by the skill man of the art. An example ofdevice for measuring the mean diameter is the Mastersizer from MalvernInstruments.

The composition is preferably in tablet or prill form.

To improve spreading and polymer diffusion in the soil, the compositioncontains a filler or a binder.

The filler is selected in a non-limiting manner, from alkali metalsulphate or chloride salts.

The binder is not limited to a single component and might comprisefunctional components. Functional binders include pesticides,fertilizers, urea, various salts of inorganic and organics acids.

Preferably the composition contains between 1 and 80% by weight offiller and more preferably between 10 and 50% by weight.

Preferably the composition contains between 1 and 50% of binder and morepreferably between 5 and 30% by weight.

Other components of the composition can be agricultural activeingredients likes natural insecticides, insecticides with organicphosphorus, insecticides with carbamates, nematicides, sterilizingagents with organic chloride, sterilizing agents with organicphosphorus, other sterilizing agents, herbicides, rodenticides.

Preferably, other components of the composition are in powder form.

For an application of the composition by airway, the bulk density of thecomposition should be preferably between 300 and 1000 kg·m⁻³ and morepreferably between 300 and 800 kg·m⁻³.

Moreover, residual water content in composition should be the lowest toavoid particles agglomeration (polymers and other components).Preferably, residual water content of the composition in particulatesshould be lower than 15 weight percent.

In a preferred embodiment, the composition is a single component whichis a water soluble or swellable polymer in powder form.

Process Description

The process of the invention consists in aerial application to the soilof a composition in particulate form.

Aerial application means application by any aerial mean but preferablyapplications are performed by airplane, helicopter, hang gliding,sailplane or drone.

The ability to apply water soluble or swellable polymers in compositionhaving a particulate form via an aerial application allows the producerto more readily use them and be much timelier in the application. Theapplication allows for flexibility and reduce the amount of labour andequipment needed to use these polymers.

In order to apply composition in particulate form by airplane, spreadersare attached to means of air transport. The spreader can be theagri-chemical spreader described in the filed patent U.S. Pat. No.4,694,991.

For a uniform application, the altitude of application of theparticulate composition is preferably below 50 m and more preferablybetween 20 m.

The amount of composition which is applied for each application to thesoil is comprised between 0.1 and 500 kg·ha⁻¹, preferably between 1 and100 kg·ha⁻¹ and more preferably between 10 and 50 kg·ha⁻¹.

The process of the invention is suitable for soil conditioning inagriculture, forestry, construction and civil engineering, mining,protection of rivers and delta against pollution, environmentalconservation, water storage or transportation.

If aerial application concerns soil conditioning in agriculture, thisapplication occurs preferably in crops fields between planting and thesubsequent first rain event or irrigation. This is the time in which thesoil is least stable.

After the first aerial application of the composition to the soil, theprocess of the invention comprises preferably additional applications.In this case, each aerial application is performed at least 20 days andnot more than 40 days after the previous one.

The process of the invention allows for the improvement in theapplication of water soluble and swellable polymer for soil erosion.Aerial application can be performed more rapidly and easily thanprevious methods.

The invention claimed is:
 1. A process for conditioning of soil tocontrol erosion by water or wind path, control formation of slackingcrusts, and preserve soil aggregate structure, comprising: applying tothe soil a composition, said composition comprising at least one of awater soluble or a water swellable polymer, the at least one polymerbeing obtained by polymerization of acrylamide and monomers with anethylenically unsaturated moiety selected from the families consistingof: anionic monomers selected from the group consisting of monomers withan acid carboxylic moiety and monomers with a sulfonic acid moiety, andnon-ionic monomers selected from the group consisting of:methacrylamide, N-alkylacrylamide, N,N-dimethylacrylamide,methylolacrylamide, vinylformamide, N-vinylpyridine, N-vinylpyrrolidone,hydroxyalkyl(meth)acrylates and (meth)acrylates with an alkoxy chain,wherein molecular weight of the water soluble polymer is above 500,000g·mol⁻¹, and wherein the composition is in particulate form, and whereinsaid applying comprises performing an aerial application of thecomposition by airplane, helicopter, hang glider, sailplane or drone. 2.The process according to claim 1, wherein the water soluble polymer hasa molecular weight between 500,000 and 30 million g·mol⁻¹.
 3. Theprocess according to claim 1, wherein the at least one of the watersoluble polymer and the water swellable polymer in the composition is inpowder or bead form.
 4. The process according to claim 1, whereinparticle size of the particulates of the composition is between 0.5 and4 millimeters.
 5. The process according to claim 1, wherein thecomposition comprises between 50% and 100% by weight of the at least oneof the water soluble polymer and the water swellable polymer.
 6. Theprocess according to claim 1, wherein the composition has a bulk densitybetween 300 and 1000 kg·m⁻³.
 7. The process according to claim 1,comprising performing at least one additional aerial application.
 8. Theprocess according to claim 7, wherein the additional aerial applicationis performed at least 20 days and not more than 40 days after a previousaerial application.
 9. The process according to claim 1, wherein amountof the composition which is applied to the soil is comprised between 0.1and 500 kg/ha.
 10. The process according to claim 1, comprisingperforming soil conditioning in agriculture, forestry, construction andcivil engineering, mining, environmental conservation, protection ofrivers and delta against pollution, water storage or transportation. 11.The process according to claim 10, comprising performing soilconditioning in agriculture, and performing the aerial application incrop fields between planting and a subsequent first rain event orirrigation.
 12. The process according to claim 1, wherein the aerialapplication is performed at an altitude below 50 m.